Chengming Zhang

Temperature Calculation for Tubular Linear Motor by the Combination of Thermal Circuit and Temperature Field Method Considering the Linear Motion of Air Gap

The air gap of tubular linear motors moves linearly, causing heat transfer states of the motor to alternate repeatedly. Thus, the heat transfer coefficients of the mover inner surface and the stator outer surface vary constantly. In this paper, the combination model of the thermal circuit and temperature field is established to calculate the transient temperature rise of a tubular linear motor with short and movable primary. The equivalent thermal circuit model of the moving air gap and the temperature field models of the primary (also named as mover) and secondary (also named as stator) are established. The thermal boundary conditions and the correlations among them are analyzed. By this method, the complicated variation and distribution of the heat transfer coefficients are gained. Moreover, the transient temperature rise of the motor is calculated. This method takes advantage of the flexibility of the thermal circuit method and the accuracy of the temperature field method. The calculated and tested results of the prototype are compared and analyzed.

Design and implementation of a loss optimization control for electric vehicle in-wheel permanent-magnet synchronous motor direct drive system

As a main driving force of electric vehicles (EVs), the losses of in-wheel permanent-magnet synchronous motor (PMSM) direct drive system can seriously affect the energy consumption of EVs. This paper proposes a loss optimization control strategy for in-wheel PMSM direct drive system of EVs which optimizes the losses of both the PMSM and the inverter. The proposed method adjusts the copper losses and iron losses by identifying the optimal flux-weakening current, which results in the PMSM achieving the lower losses in the whole operational range. Moreover there are strongly nonlinear characteristics for the power devices, this paper creates a nonlinear loss model for three-phase half-bridge inverters to obtain accurate inverter losses under space vector pulse width modulation (SVPWM). Based on the inverter loss model and double Fourier integral analysis theory, the PWM frequency is optimized by the control strategy in order to maximize the inverter efficiency without affecting the operational stability of the drive. The proposed loss optimization control strategy can quickly find the optimum flux-weakening current and PWM frequency, and as a result, significantly broaden the high efficiency area of the PMSM direct drive system. The effects of the aforementioned strategy are verified by both theoretical analysis and experimental results.

Design and Fabrication of a High-Efficiency Magnetostrictive Energy Harvester for High-Impact Vibration Systems

This paper presents the design and fabrication of a vibration energy harvester based on giant magnetostrictive material, which consists of one coil-wound Terfenol-D rod with a permanent magnet (PM) and air gap in each magnetic circuit, and the PM array on the part of a cap amplifier. In this design, cap amplifiers and variable air gap are used to increase the harvesting effect of systems under environmental impact. Modeling and simulation are developed and performed to validate the concept. The relation of magnetic field in Terfenol-D rod is derived, and its uniformity and intensity are analyzed. Then, principal design parameters of the harvester, air gap, and cap amplifiers are determined, and its static analysis of the harvesting effect is performed. In addition, a prototype is fabricated and tested. The magnetostrictive-based vibration energy harvester can generate larger voltage and power than conventional smart harvesters and they can be safely used under the impact up to 20-30 MPa.

Research on Electromagnetic and Thermal Issue of High-Efficiency and High-Power-Density Outer-Rotor Motor

The permanent-magnet synchronous motor (PMSM) with high efficiency and high power density is now attracting more and more attention, which could be largely used in occasions supplied by limited energy and restricted by weight or capacity, for example, the electric vehicles and the solar unmanned aerial vehicles. In this paper, the electromagnetic and thermal issue of a PMSM with high efficiency and high power density has been researched. We comparatively analyzed the efficiency and the power density characteristics of the outer-rotor PMSM. The influence of electromagnetic parameters on efficiency and power density has been analyzed. Through researching the Halbach array, we got the maximum output torque and the minimum core loss. Because of the inner stator, the heat generated by the winding has much trouble to dissipate. The thermal-transfer structure based on the heat pipe has been proposed, which could decrease the temperature of windings by more than 180 °C shown by finite-element analysis results. Finally, the prototype motor has been made, and the experimental results are consistent with the analysis, which verified the correctness of the theory.

Effect of structure parameters on the losses and efficiency of Surface-Mounted PMSM

Due to the advantages of high efficiency and high torque density, the Permanent Magnet Synchronous Machine (PMSM) has been widely used in direct-drive applications such as all-electric propulsion system. The loss and efficiency of PMSM are the main restriction for performance improvement. This paper focuses on analyzing the influence of structure parameters on the loss and efficiency of PMSM, including the split-ratio, the thickness of PMs, the pole-slot combination and the utilization of Halbach PM array, based on the Magnetic Circuit Method (MCM). The variation of the loss with the changing of parameters can provide some guidance for high-efficiency motor design. And the results of Finite Element Analysis (FEA) prove the correctness of MCM.

Design and Implementation of a Loss Optimization Control for Electric Vehicle In-Wheel Permanent-Magnet Synchronous Motor Direct Drive System☆

Abstract As a main driving force of electric vehicles (EVs), the loss of in-wheel permanent-magnet synchronous motor (PMSM) direct drive system can seriously affect the energy consumption of EVs. This paper proposes a loss optimization control strategy for EV in-wheel PMSM direct drive system which can optimize both the loss of PMSM and loss of inverter. The proposed method adjusts the copper loss and iron loss by optimal flux-weakening current, and as a result the PMSM achieve the lower loss in the whole operation range. According to the speed, the PWM frequency is optimized by the proposed control strategy, which can acquire high efficiency of inverter and not affect the stability of the PMSM system in the each operation condition. The optimum flux-weakening current and PWM frequency can be quickly found, and optimal effects of energy loss are verified by theoretical analysis and experimental results.

Accurate Prediction of Leakage Flux Boundaries for an Axial-Flux MEMS Micromotor Design

This paper presents an axial-flux microelectromechanical systems micromotor with dual-rotor and 10 mm diameter. The leakage fluxes are a large proportion of the total flux due to the micro dimension. Therefore, an accuracy prediction of the boundaries of leakage fluxes is vital for motor design. Response surface methodology is well adapted to obtain empirical formulas of the boundaries of the leakage fluxes in this paper. Additionally, an improved pigeon-inspired optimization algorithm is used to efficiently search the coefficients of the second-order empirical formulas. The feasibility of the proposed method is validated by the three-dimensional finite element analysis. Finally, the method is applied to accurate design one micromotor.

Design and construction of magnetostrictive energy harvester for power generating floor systems

In this paper, a new prototype of magnetostrictive-based vibration energy harvester for power generating floor systems is presented, and its structure is constructed. The harvester utilizing the Villari effect (inverse-magnetostrictive effect) consists of a coil-wound Terfenol-D rod. To generate more electrical power, a PM (fixed on the part of cap amplifier) and variable-length air-gap are designed in each magnetic circuit, which helps to enlarge Villari effect in Terfenol-D rod in the action of environmental vibration. The magnetic field and its leakage in harvester are analyzed, and principal design parameters of harvester are optimally determined. Then, a prototype is fabricated and tested, and its harvesting effect is calculated. The harvester exhibits high power density, can generate up to 0.022 T/MPa piezomagnetic effect and safely used in up to 20MPa transient impact.

An improved predictive current control for PMLSM considering parameter variation

For the model-based control strategy, the predictive current control (PCC) requires the full knowledge of the motor parameters, which reduces the system robustness. This paper presents an optimal PCC for the permanent magnet linear synchronous motor (PMLSM). Through the information of first two switching periods, the parameter variation issue can be eliminated without impacting the performance of the current loop. The simulation and experimental results are shown to prove the correctness and effectiveness of the proposed scheme.

Magnetostrictive energy generator for harvesting the rotation of human knee joint

This paper presents the design and fabrication of a rotary-impact magnetostrictive energy generator, used to harvest the rotation of human knee joint. The harvester consists of twelve movable Terfenol-D rods, surrounded by the picked up coils respectively, and alternate permanent magnet (PM) array sandwiched in each part of the shell. Rotational electromagnetic power generating effect and impacted magnetostrictive power generating effect are designed in the harvester. Modeling and simulation are used to validate the concept. Then, magnetic field and leakage of the harvester are analyzed, electromagnetic force in the harvester is simulated. A prototype of harvester is fabricated, and subjected to the experimental characterization. It can be concluded that huge induced voltage generated in the short-time impact situation and that induced voltage in the harvester can reach up to 60-80 volts at 0.91Hz low frequency rotation. Also, the presented harvester has good harvesting effects at low frequency human walk...